The present invention relates generally to a harvester for harvesting crops such as corn.
Conventional harvesters for harvesting crops such as sweet corn, seed corn or field (animal feed, etc.) corn, use corn heads which utilize unit gear system which drives both the knives (or stock rolls) and gathering belts (or chains). These systems used dependent drive systems to drive the knives and the gathering belts. An example of such a system is described in U.S. Pat. No. 4,227,366 incorporated by reference. Older harvesters used independent drive systems to drive the knives and gathering belts, but lacked independent control systems for the knives and gathering belts. Optimizing harvesting parameters using these harvesters is impossible, since many environmental factors influences optimum knife speed and different environmental factors affect optimum gathering belt speed. Optimum knife speed may be affected by crop population, crop height, dryness and insect infestation. Optimum gathering belts speed may be affected by harvester ground speed, which is affected by ground conditions such as terrain, mud, rocks and ditches. The dependent speeds between the knives and the gathering belts prevents independent adjustment of the speeds to match the environment, causing a less efficient operation resulting in reduced yields, damage to the product, reduced cleaning, and reduced machine effectiveness, causing reduced life of the machine and higher maintenance costs.
The optimum gathering belt speed is approximately equal to the ground speed of the harvester. However, ground conditions may dictate a slower ground speed, which would require that the gathering belt speed be slowed down. If the gathering belt speed is not made slower, the gathering belts will aggressively pull corn stalks into the corn head, resulting in higher gathering belt wear. This also causes excessive stalk breakage, which results in an increase in load trash (leaves and stalks).
Another condition in which optimum gathering belt speed may be slower than conventional corn head gathering belt speed occurs when the corn stalks are extremely tall or densely spaced. The harvester must be operated at a slow ground speed to allow the knives and cleaning system to harvest the crop. In this slow ground speed mode, the gathering belt must also be slow to prevent the abrasion and stalk breakage described above.
A third condition in which ground speed may be slower than a conventional gathering belt speed is when the crop is lodged (the stalks are lying down) caused by wind or insects. If the gathering belt speed is higher than ground speed, the gathering belt will break and dislodge the stalks, yielding excess trash in the load.
A fourth condition may occur, which the harvester may travel at a higher speed than normal, such as when the stalks are sparsely populated, the stalks are short, and the ground conditions are good. In this case, the gathering belt speed needs to be faster than the conventional gathering belt speed, to match the ground speed.